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Abstract
Chromium, manganese and molybdenum exhibit a high hardening effect, especially with carbon, and therefore offer a considerable potential for powder metallurgy production of sintered and sinter hardened highly stressed precision steel parts. The object of the investigation was to study the effect of a 1–3% manganese addition and of manganese carrier grades on as sintered and as sinter hardened properties of prealloyed Fe–3Cr–0·5Mo steel with low carbon content. The sintering of the samples was carried out at 1250°C in cracked ammonia with a dew point −30°C at the cooling rate of 0·06°C s−1, and sinter hardening at the mean cooling rate 0·3°C s−1. The tensile, bending and impact strength, hardness and microstructures of the steels were determined and analysed. The highest values of the mechanical properties were obtained for alloys with 2% manganese added as medium carbon ferromanganese, in both the sintered and sinter hardened state. Heterogeneous microstructures rate, containing martensite, bainite, pearlite and even ferrite in dependence on manganese addition and cooling rate was characteristic for these steels.